I was very apprehensive about my connection through Houston to Merida last month because I had read a couple of reviews saying the Houston airport was chaotic and took hours to navigate. So I was positively pleased when we had no problems at all coming and going through Houston. We had a two-hour layover going to Merida, which gave us time to have dinner and change dollars for pesos, and a couple of hours coming back. We managed to get through customs, find our way to the next gate, and pick up breakfast at Starbuck's to take on the plane.
I can't imagine flying to Cancun, which was suggested, and then having a 4-hour drive or bus trip to Merida. We had a 15 minute taxi ride from the airport to our hotel in Centro. It was one of the easiest travel experiences I've had going to Mexico.